1. Field of the Invention
The present invention relates to a small watercraft, and in particular to the arrangement of heat-sensitive components in the watercraft.
2. Description of Related Art
Personal watercraft have become popular in recent years. This type of watercraft is quite sporting in nature and is designed to carry a rider and possibly one or two passengers. A relatively small hull of the personal watercraft commonly defines a rider's area above an engine compartment.
An internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The jet propulsion unit is located within the tunnel and is driven by a drive shaft. The drive shaft commonly extends between the engine and the jet propulsion device, through a wall of the hull that forms a front gullet portion of the tunnel.
Personal watercraft often employ an in-line, multi-cylinder, crankcase compression, two-cycle engine, usually including two or three cylinders. The engine conventionally lies within the engine compartment with the in-line cylinders aligned along a longitudinal axis of watercraft hull (in the bow-stern direction).
An exhaust system of the personal watercraft discharges engine exhaust to the atmosphere either through or close to the body of water in which the watercraft is operated. Although submerged discharge of engine exhaust silences exhaust noise, environmental concerns arise. These concerns are particularly acute in two-cycle engines because engine exhaust from two-cycle engines often contains lubricants and other hydrocarbons.
Such environmental concerns have raised a desire to minimize exhaustion of hydrocarbons and other exhaust byproducts (e.g., carbon monoxide and oxides of nitrogen) and thus reduce pollution of the atmosphere and the body of water in which the watercraft is operated. In response to increased concerns regarding exhaust emission, some personal watercraft have become equipped with a catalyzer to convert exhaust byproducts to harmless gases.
Catalyzers must operate at a relatively high temperature in order for the necessary thermal reaction and burning of the exhaust byproducts to occur. A catalyzer thus desirably operates within a specific range of temperature so as to effectively and efficiently convert engine exhaust into generally harmless gases. The catalyzer thus often lies near the engine in order to operate at elevated temperatures.